The invention relates to a method for the further processing of industrial residue discharges from molasses processing, for example of vinasse (slop) or residual molasses, by means of ion-exclusion chromatography.
During molasses processing there is obtained as an industrial residue discharge in particular vinasse or slop or residual molasses. Said products have been utilizable only with difficulty to date and their disposal also presents problems.
An initial aim of the invention therefore consists in proposing a method for further processing with which the amounts to be disposed of may be reduced and/or components which are still utilizable economically be obtained.
Betaine, for instance, could be considered as an important component of such industrial residue discharges.
Betaine ((CH.sub.3).sub.3 --N.sup.+ --CH.sub.2 --COO.sup.-, C.sub.5 H.sub.11 NO.sub.2) occurs in various plant species, but above all in sugar beet. During the obtaining of sugar from sugar beet the betaine accumulates in the molasses; the concentration lies in the range from 3 to 8% betaine in the dry matter.
Also during many biotechnological processes with molasses as raw material (source of carbon), e.g. during the production of yeast or alcohol, betaine is not assimilated and therefore accumulates in the final discharges of said processes, for instance in the vinasse (molasses slop). The betaine concentrations may further-more amount to more than 15% of the dry matter.
Similar concentrations are also found in the residual molasses during processes for the desugarizing of molasses, e.g. according to the barium sulphate or Steffen process.
Because of its property as a methyl group donor, betaine is used mainly as an additive for feedstuffs. In addition, however, betaine is also used in cosmetic and pharmaceutical preparations, for instance as a skin care agent or a liver protection preparation.
Various methods have been developed for the obtaining of betaine. The latter including obtaining by crystallization as hydro-chloride, by extraction with the aid of organic solvents, by ion exchange and in particular by means of ion-exclusion chromatography, as proposed for example in EP 0 054 544 B1.
Said method tested many times in practice for the obtaining of betaine from molasses takes place as follows: A cationic exchanger is loaded with the solution to be processed. In so doing the molasses is diluted to such an extent that it possesses a solids content in the approximate range of 20 to 50%. In the cationic exchanger two effects essentially take place simultaneously side by side, ion exclusion and the molecular sieve effect. The strong electrolytes migrate relatively undisturbed through the separating column, while the weak electrolytes and non-electrolytes are adsorbed by the exchanger. Due to the elution with water the absorbed substances are released again. In addition, due to the different rates of migration through the exchanger, the electrolytes and non-electrolytes are separated from one another, and fractions of different compositions are obtained.
Whereas the diluted molasses is passed as a uniform charge onto the top side of a separating column, the various substances appear in a spaced time sequence after passing through the separating column. Since the components of the original substance are essentially constant and known, it may also be predicted with a high degree of accuracy which components will appear in the outlet of the separating column and when, so that the individual fractions may be deliberately separated from one another.
Although the fractions of the various charges are of constant composition, they may nevertheless be optimized in a suitable manner within certain limits by deliberate choice of the process parameters.
Completely accurate separation of the components is however not possible; there are certain mixed amounts between the individual fractions in each case.
The current methods start from the fact that discharges from sugar beet processing, such as e.g. molasses, are purified by multiple separation according to the ion-exclusion method with water as eluent. The use of water helps to ensure as clean a separation as possible of the individual fractions from one another and keeps the "mixed discharges" relatively small. If other eluents were to be used, additional impurities would also be introduced, and this has therefore been refrained from to date.
Despite the intrinsically good results of the known method it is disadvantageous that high evaporation and processing costs are incurred, since at the outlet of the separating column the individual fractions contain large amounts of water. As a result, the obtaining of the valuable components, in particular betaine, from industrial residue discharges is not always economic. This applies in particular to the processing of vinasse or residual molasses, where a further cost unit is not available as in the case of the obtaining of sugar from molasses.
It is therefore a further aim of the invention to develop the generic method in such a way that a more cost-effective obtaining of betaine is possible also from such residue discharges.